Biology Basics – Study Notes
(For Karnataka Patwari / Lekhpal – General Awareness & Current Affairs)
1. Simple Explanation
Biology is the science that studies living organisms—how they grow, reproduce, evolve, and interact with each other and the environment.
- Life is defined by a set of characteristics: metabolism, growth, response to stimuli, reproduction, and evolution.
- All living things are built from cells – the basic structural and functional units of life.
- Biological information is stored in DNA and passed down through genes.
- Organisms are grouped into a hierarchical classification (Kingdom → Phylum → Class → Order → Family → Genus → Species).
- The ecological pyramid shows how energy flows from producers (plants) to consumers (herbivores, carnivores) and decomposers (fungi, bacteria).
2. Key Points
| Area | Main Ideas | Example / Note |
|---|---|---|
| Cell Theory | 1. All life is made of cells. 2. Cells are the smallest units of life. 3. All cells arise from pre‑existing cells. |
Mitosis & meiosis illustrate cell division. |
| Cell Structure | Prokaryotic: no nucleus, simple. Eukaryotic: nucleus, organelles (mitochondria, chloroplasts). |
Plant cells have chloroplasts; animal cells have centrosomes. |
| DNA & Genes | DNA is a double‑helix that stores genetic code. Genes are DNA segments that code for proteins. |
The human genome has ~23,000 genes. |
| Genetics Basics | Alleles: different forms of a gene. Genotype: genetic makeup. Phenotype: observable traits. Inheritance follows Mendelian rules (dominant, recessive). |
Red flower (RR) + white flower (rr) → all pink (Rr) in F1. |
| Evolution | Natural selection, mutation, gene flow, genetic drift. | Darwin’s finches – beak size adapts to food source. |
| Ecology | Producers: autotrophs (photosynthesis). Consumers: heterotrophs (herbivores, carnivores). Decomposers: bacteria, fungi. |
Food chain → Food web. |
| Human Body Systems | Digestive, circulatory, nervous, respiratory, excretory, endocrine, immune, musculoskeletal. | Heart pumps blood → oxygen transport. |
| Health & Hygiene | Importance of vaccination, sanitation, nutrition. | Handwashing reduces diarrheal disease by >50 %. |
| Current Affairs (2024) | • WHO declared X as a new disease. • India’s National Health Mission launched AI‑based diagnostics. • Advances in CRISPR gene editing for sickle cell disease. |
Keep up with latest govt. health schemes. |
3. Worked Example – Mendelian Genetics
Problem:
A pea plant that carries the dominant allele for yellow seed colour (Y) is crossed with a plant that carries the recessive allele for green seed colour (y).
- What are the possible genotypes and phenotypes of the F1 generation?
- If an F1 plant is crossed with another plant that carries the recessive allele (y), what is the ratio of yellow to green seeds in the F2 generation?
Solution
| Step | Explanation | Result |
|---|---|---|
| 1. Parental genotypes | Yellow (Yy) × Green (yy) | |
| 2. Gametes produced | Y, y from Yy plant; y from yy plant | |
| 3. Punnett square (F1) | ||
| Y | ||
| y | ||
| 4. F1 genotypes | 1 × YY, 2 × Yy, 1 × yy | |
| 5. F1 phenotypes | Yellow (YY & Yy) : Green (yy) | 3 Yellow : 1 Green |
| 6. F1 × yy cross | Genotype of F1 (Yy) × yy | |
| 7. Punnett square (F2) | ||
| y | ||
| y | ||
| 8. F2 genotypes | 4 × yy | |
| 9. F2 phenotypes | 4 × green (since yy only) | 0 Yellow : 4 Green |
Answer:
- F1: 3 yellow : 1 green (genotypes: 1 YY, 2 Yy, 1 yy).
- F2: 0 yellow : 4 green (all recessive phenotype).
4. Quick Revision Summary
- Cell – the universal unit of life.
- DNA – genetic blueprint; genes encode proteins.
- Mendelian inheritance – dominant vs recessive, genotype → phenotype.
- Ecological pyramid – energy flow from producers to consumers to decomposers.
- Human systems – each body system has a distinct function (e.g., heart → circulation).
- Public health basics – vaccination, sanitation, balanced diet.
- Current affairs tip – stay updated on national health schemes and new scientific breakthroughs (e.g., CRISPR, AI diagnostics).
Use this cheat‑sheet before exams, and refer back to the worked example whenever you need a refresher on genetics. Good luck!